Okay I've read a bunch of past threads and I think I have this down but need some confirmation as I am a relative newbie. I bought a 1994 DR250SES third hand. It has an aftermarket Acerbis desert tank. Ever since I bought it it has been sluggish starting in 1st gear, at least until RPM's are up. A couple of months after purchase, and not a ton of riding, it started really hesitating, stuttering you might say. I have pulled and cleaned the carb 3 times, inspected the diaphragm (fine) and each time it seems like its fixed, only to start the whole thing over again. I have even removed the petcock and inspected it to see if the filters were blocked. They were fine. Yesterday, on a dirt ride with my son, it really started acting up, but really only after it got hot. It would stutter and hesitate on acceleration. We hit the pavement for a return to the vehicle and it just flat out died, and no amount of holding the clutch in and revving would bring it back. It seemed out of fuel. I let it sit a minute or two, it started up, and I got it to the car at high speed, but it still hesitated in first gear when I started out.
So--I think this is my problem: The aftermarket tank does not a have a vacuum line on the petcock and the vacuum port on the carb has been blocked. The boggy/hesitation in first gear especially seems like a symptom of the lack of vacuum, since I understand that is what the vacuum line is supposed to address--giving a quick shot of fuel to the carb on quick acceleration when the carb can loose vacuum momentarily (is this right?). As to why it seem to be more fuel starved after it heats up---I am at a loss unless it too is related to the absence of the vacuum line.
Am I right?